The present invention, in some embodiments thereof, relates to waste material treatment and, more particularly, but not exclusively, to treatment of waste material using at least two bioreactors.
A large amount of interest in treatment of municipal and industrial wastewaters has arisen as a result of environmental pollution concerns. Often in treatment of wastewater from industrial and municipal sources, the activated sludge process is employed for treatment and purification.
The biological treatment process takes advantage of the ability of bacteria to use wastewater constituents to provide the energy for microbial metabolism and the building blocks for cell synthesis. The metabolic activity removes contaminants from the wastewater. The process generally consists of maintaining an aeration basin in which wastewater is fed to a suspension of bacteria to form a mixed liquor. The mixed liquor is aerated to furnish oxygen for the respiration of the biomass which assimilates and metabolizes the biological oxygen demand of the wastewater. After a suitable period of aeration, the mixed liquor is introduced to a clarifier in which the biomass settles and the treated wastewater overflows into a receiving stream. A portion of the settled biomass, which is concentrated at the bottom of the clarifier, is recycled to the aeration basin, and a portion is purged in order to maintain a desired biosolids inventory within the system (e.g. based on F/M).
Variations in flow rates, organic (e.g. phenols) or non-organic (e.g. salinity) concentrations or other conditions cause fluctuations in influent wastewater quality and quantity e.g. contamination level. In particular, certain industrial events can result in the loading of an organic or non-organic shock pollutant load into the treated wastewater collection system. Such shock loading can upset the balance of the microbial culture in the process with a resulting loss of wastewater treatment effectiveness. Following an upset a prolonged period of several weeks or even months is required to bring the system back to steady-state operations.
Numerous techniques have been proposed for improving the activated sludge process, these include U.S. Pat. Nos. 6,555,002, 5,646,863, 5,779,911, 6,023,223, 6,596,171 and 6,625,569; and Leu et al., 2009, “Modeling the Performance of Hazardous Wastes Removal in Bioaugmentated Activated Sludge Processes,” Water Environment Research, 81, 11, 2309-2319.